class Stack:
    def __init__(self):
        self.__stack = []
    
    def pop(self):
        if self.__stack:
            return self.__stack.pop()
        return None
    
    def push(self, data):
        self.__stack.append(data)
    
    def get_top(self):
        if self.__stack:
            return self.__stack[-1]
        return None